The present invention relates to an electronic shutter for a camera and a method for controlling the same and, more particularly, to an electronic shutter with a large aperture and a control method thereof that can maintain a closed state of a sector even when outer shock is applied in a state where a main switch is turned Off, thereby improving the reliability of the camera.
Generally, an electronic shutter of a camera has an automatic focusing function for adjusting the focus by measuring a distance to a subject and adjusting the position of a focus lens in response to the measured distance, and an automatic exposure function for adjusting the exposure of the camera by adjusting the combination of an iris speed and a shutter speed with respect to the optimum exposure amount of the subject.
Such an electronic shutter for a camera is disclosed in Korean Patent Nos. 10-015918 and 10-0180326 and Korean unexamined Patent No. 10-1999-015918.
The Korean Patent Nos. 10-0157516 and 10-1999-015918 disclose an electronic shutter that is designed to conduct the automatic focus and exposure functions by plural arc-shaped drive motors. The electronic shutter comprises a mechanical structure for receiving a lens barrel. The arc-shaped drive motor has a problem that a large space of a motor base is occupied by a stator and a rotor, deteriorating the freedom of design.
The Korean Patent No. 10-0180326 discloses an electronic shutter having plural can-shaped drive motors for realizing the automatic focusing and exposing. An exposure structure of the electronic shutter comprises three sectors to realize a large aperture. The can-shaped drive motor and the exposure structure having the three sectors are proposed to solve the problem of the arc-shape drive motor. However, when outer shock is applied in a state where a main switch of the camera is in an off-state, the sectors may be inadvertently opened to expose the film, thereby deteriorating the reliability of the camera.
Therefore, the present invention has been made in an effort to solve the above-described problems.
It is an objective of the present invention to provide an electronic shutter for a camera, which can minimize the space occupied by a stator and a rotor, thereby increasing the freedom of design.
It is another objective of the present invention to provide an electronic shutter that can realize a large aperture by employing three sectors in an automatic exposure structure.
It is a still another objective of the present invention to provide an electronic shutter control method that can remarkably reduce an error in an initial position of the shutter by improving the initial position setting method.
To achieve the objectives, the present invention provides an electronic shutter for a camera, comprising first driving force generating means for generating driving force for moving a lens barrel in a direction of an optical axis; lens barrel moving means for moving the lens barrel by use of driving force from the first driving force generating means; adjusting means for adjusting a focus ring to an initial position when electric power is applied or a shutter release operation is applied; second driving force generating means for generating driving force for driving at least one sector; sector opening/closing means for opening and closing the sector by use of driving force from the second driving force generating means; and exposure position detecting means for detecting an exposure position by cooperating with the sector opening/closing means, the exposure position detecting means comprises a photo reflector located preferably on a motor base; a reflecting plate located preferably on a shutter base; and an open lever rotatably coupled preferably on the shutter base, the open lever including a projection disposed between the photo reflector and the reflecting plate and rotating in response to rotation of the exposure ring.
Preferably, the lens barrel moving means comprises plural speed reduction gears mounted on the shutter base to receive driving force from the first driving force generating means and reduce rotational force; a power transmission gear rotating by receiving the rotational force from the speed reduction gears; and a focus ring coupled on the shutter base to be rotatable by the rotational force from the power transmission gear, the focus ring being provided at its inner circumference with a helicoids groove in which the lens barrel coupled to be movable in the direction of the optical axis.
Preferably, the sector opening/closing means comprises a gear rotating by the second driving force generating means; a connection gear engaged with the gear to move within a predetermined section of the shutter base by receiving rotational force from the gear, the connection gear being provided with at least one projection extending in the direction of the optical axis; an exposure ring rotatably coupled to the shutter base, the exposure ring being provided with a hook projection that can be limited in rotation by contacting the projection of the connecting gear, a projection fitted in the sectors to move the sectors and a gear formed on its outer circumference; an open lever engaged with the gear of the exposure ring to rotate together; and an open lever spring having a first end elastically supported on the open lever and a second end elastically supported on the shutter base.
Preferably, the first driving force generating means and the second driving force generating means are formed of a can-type stepping motor.
According to another aspect of the present invention, an electronic shutter for a camera comprises first driving force generating means for generating driving force for moving a lens barrel in a direction of an optical axis; lens barrel moving means for moving the lens barrel by use of driving force from the first driving force generating means; adjusting means for adjusting a focus ring to an initial position when electric power is applied or a shutter release operation is applied; second driving force generating means for generating driving force for driving at least one sector; sector opening/closing means for opening and closing the sectors by use of driving force from the second driving force generating means; exposure position detecting means for detecting an exposure position by cooperating with the sector opening/closing means; and sector open preventing means for preventing the sectors from opening when outer shock is applied in a main power-off state.
Preferably, the first driving force generating means and the second driving force generating means are formed of a can-type stepping motor.
Preferably, the lens barrel moving means comprises plural speed reduction gears mounted on the shutter base to receive driving force from the first driving force generating means and reduce rotational force; and a focus ring coupled on the shutter base to be rotatable by the rotational force from the reduction gears, the focus ring being provided with a projection extending toward the direction of the optical axis to rotate and move the lens barrel, helicoid-coupled to the shutter base, in the direction of the optical axis.
Preferably, the sector opening/closing means comprises a lever rotating by the first driving force generating means, the lever being provided with a projection extending the direction of the optical axis at an eccentric location; a first open gear rotatably surface contacting the projection of the lever, the first open gear being provided at its outer circumference with a gear and rotatably coupled on the shutter base; a second open gear coupled to the shutter base and engaged with the gear of the first open gear; an open lever coupled on the shutter base to be rotatable by the rotational force of the second open gear, the open lever being provided with a projection in the direction of the optical axis; an open lever gear for receiving the rotational force by the projection of the open lever; an exposure ring coupled on the shutter base to be rotatable by the rotational force of the open lever gear, the exposure ring being provided with a projection fitted in the sectors to move the sectors; and an open lever spring having a first end elastically supported on the open lever and a second end elastically supported on the shutter base.
Preferably, the exposure position detecting means comprises a photo reflector located on a motor base; a reflecting plate located on a shutter base; and an open lever rotatably coupled on the shutter base, the open lever being provided with a projection disposed between the photo reflector and the reflecting plate and rotating in response to rotation of the exposure ring.
Preferably, the sector open preventing means comprises a focus ring rotatably coupled on the shutter base and provided with a hook step in the direction of the optical axis; and an open lever rotatably coupled on the shutter base and provided with a suppression end projected in a radial direction so as to selectively contact the hook step of the focus ring.
According to still another aspect, the present invention provides a method for controlling an electronic shutter for a camera, comprising the steps of (S1) clearing counter_1 and counter_2 values detected by the photo interrupter 8 to a value xe2x80x9c0xe2x80x9d; (S3) controlling driving pulse such that a focus ring rotates counterclockwise by driving a stepping motor; (S5) determining if the detected value of the photo interrupter is a high value; (S7) increasing the counter_1 value by 1 when the value detected by the photo interrupter is the high value; (S9) determining if the increase value of counter_1 is consecutively detected above predetermined times; (S11) controlling the pulse such that the focus ring rotates clockwise when the value of the counter_1 is increased as many as the predetermined times; (S13) determining if the value detected by the photo interrupter is a low value; (S15) determining if the value applied to first and third coils of the stepping motor is the high value when the determined value is the lower value; and (S19) turning Off power of the stepping motor when the condition of the step (S15) is satisfied.
The method further comprises the step of returning the control procedure to the step (S3) when the increase value of counter_1 is not consecutively detected above the predetermined times in the step (S8).
The method further comprises the step of returning the control procedure to the step (S11) when the determined value is not the low value in the step (S13).
The method further comprises the step of (S17) controlling the pulse to rotate the focus ring clockwise when the value is not the high value in the step (S15) to return the control procedure to the step (S15).
The method further comprises the steps of (S21) increasing the counter_2 value by 1 when the valve detected by the photo interrupter is not the high value in the step (S5); (S23) determining if the counter_2 value is above predetermined value; (S25) controlling the focus ring to rotate clockwise when the condition of the step (S23) is satisfied in the step (S23); (S27) determining if the value detected by the photo interrupter is the high value; (S29) increasing the counter_1 value by 1 when the value is the high value in the step (S27); and (S31) determining if the value of the counter_1 is above a predetermined value and when this condition is not satisfied, the control procedure is returned to the step (S25), and when satisfied, the control procedure is returned to the step (S13).
The method further comprises the step of returning the control procedure to the step (S3) when the counter_2 value is above the predetermined value in the step (S23).
The method further comprises the step of keeping driving the focus ring clockwise when the value is not the high value in the step (S27).